1. Field of the Invention
The present disclosure relates to a liquid crystal display device and, more particularly, to a device having an improved thin film transistor (“TFT”) substrate.
2. Description of the Related Art
A liquid crystal display (“LCD”) device includes a liquid crystal panel displaying an image, a panel driving unit driving the liquid crystal panel, and a light source providing light to the liquid crystal panel. The panel driving unit includes a gate driving unit driving gate lines and a data driving unit driving data lines. The gate driving unit supplies a scan signal to the gate lines sequentially, and the data driving unit supplies a data voltage to the data lines when the scan signal is applied.
The liquid crystal panel includes a TFT substrate on which a TFT array is formed, a color filter substrate on which a color filter array is formed, and liquid crystals formed between the TFT substrate and the color filter substrate.
The color filter substrate includes a black matrix defining a sub-pixel area, and preventing light leakage, a color filter formed in the sub-pixel area and displaying red, green or blue color, and a common electrode receiving a common voltage.
The TFT substrate includes gate lines and data lines intersecting each other, TFTs formed at intersections between the gate lines and the data lines and connected to the gate lines and the data lines, and pixel electrodes connected to the TFTs. Moreover, the TFT substrate includes an ESD protection circuit protecting the TFT array. The ESD protection circuit includes at least one protection TFT, and the channel length of the protection TFT constituting the ESD protection circuit is formed large.
The TFT substrate is formed using a 4-mask process, in which a gate insulating layer, a semiconductor layer, an ohmic contact layer and a data pattern are formed using a single half-tone or slit mask to form a channel of the TFT.
However, the slit mask and the halftone mask are expensive and the slit mask has a high defect rate due to differences in the amount of light exposure in the slit area. Furthermore, it is very difficult using a slit mask to form a uniform channel of less than 3 μm.